本研究之目的為發展新濕式成膜技術並製備具良好皮層之非對稱中空纖維膜，並應用於滲透蒸發分離乙醇/水溶液，新發展技術可分為外皮層(outer skin layer)及內皮層(inner skin layer)控制技術，外皮層控制技術主要分成兩部分，其一利用延遲定型方式於PSF/NMP 紡絲液中加入非親水性(油性)溶劑(氯仿，chloroform)形成共溶劑系統，利用紡絲條件(濕式紡絲及乾/濕式紡絲)變化增進延遲定型效果，製備所需中空纖維膜之結構，研究中探討中空纖維膜結構型態對滲透蒸發分離乙醇/水溶液效能之影響，另一外皮層控制技術之方法為控制外部凝聚劑(External coagulant)極性用以增進薄膜延遲定型效果，研究中利用光穿透性試驗，探討不同極性之凝聚劑對薄膜延遲定型效果，並分析控制外部凝聚劑極性所製備之非對稱中空纖維膜結構型態對滲透蒸發分離乙醇/水溶液效能之影響。內皮層控制技術是以控制蕊液(Bore liquid)之極性大小達成對紡絲液延遲定型效果用以製備具良好內皮層之非對稱中空纖維膜，研究中利用光穿透性試驗，探討不同極性之凝聚劑對薄膜延遲定型效能之影響，並探討中空纖維膜製備過程中不同極性之蕊液對分子(PSF)及不同磺酸化程度高分子(SPSF)中空纖維膜結構及滲透蒸發分離乙醇/水溶液效能之影響。
外皮層控制技術第一部分之研究結果發現PSF/NMP紡絲系統中添加入氯仿，以濕式紡絲法成膜並以去離子水作為凝聚劑時，中空纖維膜因氯仿而延遲定型，使纖維膜中之巨型孔洞雖因溶劑添加有受到抑制，但其皮層緻密程度不足，因而促進滲透蒸發分離之選擇性上升不明顯，而當以乾/濕式紡濕法於添加共溶劑(氯仿)系統中，於有氣距(Air gap)條件下，能使外皮層高分子濃度有效增加形成高分子富相，隨後當初紡中空纖維進入凝聚劑(去離子水)進行(溶劑/凝聚劑)相轉換時因延遲定型效應能增進外皮層之緻密性與連續性，使得所製備之中空纖維膜具有緻密性外皮層與孔隙性內皮層構造，外皮層巨孔明顯變小形成海綿性結構，研究發現紡絲液中氯仿添加會顯著影響膜結構與分離效能，其中空纖維膜之紡製條件亦會顯著影響其中空纖維膜的結構型態與分離效能。當紡製時氣距長度增加，高分子鏈順向排列較緊密，所形成中空纖維膜結構較緻密，經由上述結果可得知，有效利用延遲定型與紡絲條件可以製備出緻密之外皮層結構並有效提升滲透蒸發效能。外皮層控制技術第二部分主要為控制外部凝聚劑極性增進延遲定型效應之研究，依據光穿透研究結果指出低極性之正丁醇為凝聚劑時有最佳延遲定型效果，能有效使中空纖維膜外皮層結構形成緻密外皮層，並有效提昇滲透蒸發分離乙醇/水溶液之效能。
內皮層控制技術研究結果顯示以低極性之正丁醇為蕊液時有最佳延遲成型效果，同時能有效使中空纖維膜內皮層結構形成緻密內皮層
，並有效提昇滲透蒸發分離乙醇/水溶液之效能。研究中進一步使用正丁醇為蕊液應用於製備不同磺酸程度之PSF非對稱中空纖維膜時，研究結果證實正丁醇為蕊液對磺酸化高分子(SPSF)延遲效能較不顯著，導致分離效能降低，因此進一步降低其極性，當蕊液組成為正己烷及正丁醇(vol. 1:1)比例之混和液時因極性改變，能有效延緩磺酸化薄膜之成型時間並獲所需之內皮層結構，同時應用於滲透蒸發分離時亦能明顯改善磺酸化中空纖維膜之滲透蒸發效能。
上述之研究成果可得知，利用溶劑(氯仿)之添加或改變蕊液極性可製備出不同孔隙結構之內外皮層結構中空纖維膜，考量不同極性溶劑為外部凝聚劑，雖也可製備出不同孔隙膜結構，但其溶劑消耗量卻極大不利於大量生產，因此利用少量溶劑添加及不同極性蕊液做為控制皮層結構之方法，製備出具不同外皮層及內皮層構造之中空纖維膜技術，其具商業化之價值。 The purpose of this investigation is to develop new wet phase inversion technologies for hollow fiber membrane preparation and applied those membranes for dehydration of water/ethanol mixtures by pervaporation. The new technologies include outer skin layer control and inner skin layer control method of the asymmetric hollow fiber membranes. In the case of outer skin layer control system, the delay demixing technology was used to dominate the outer skin layer thickness of hollow fiber membranes by addition of co-solvent in casting solution and air gap control in the membrane preparation. The control of coagulation polarity is another method to dominate the outer skin layer structure of hollow fiber membrane. Light transmittance measurements were made to explore the influence on the delay demixing behavior of casting solution in the membrane formation. The effects of membrane formation pathways on the cross section structure and separation performance of hollow fiber membranes were also investigated in this study. In the case of inner skin layer control system, the bore liquid control and considering on the polarity of bore liquid were investigated for the delayer demixing behavior in the membrane formation. Polarity of bore liquids is one of the importance factors to dominate the delay demixing behavior of inner skin layer in membrane formation. Increase the delay demixing time of the casting solution enhanced the skin layer thickness of hollow fiber membranes and altered the membrane cross section structures. The polarity of polymer was also considered in this case and the separation performances for dehydration of ethanol/water mixture were also discussed.
In the first part, the macro pore development was inhibited by the delay demixing of casting solution with adding chloroform and H2O as the coagulant in membrane formation. It was found that defects formed on the outer skin layer and induced the low separation factor of hollow fiber membranes. By considering the air gap to improve skin layer formation, the chloroform vaporized in the air and then enriched the polymer concentration of outer layer casting membrane with chloroform addition in casting solution. The rich polymer concentration effectively increased the skin layer thickness and decreased defects on the surface of hollow fiber. The observation of fiber cross section indicated that the dense skin layer and sponge sublayer were formed by using this method. while the increase the air gap distance, orientation of polymer chain in casting solution were found and affected the skin formation. By using the above technologies, the optimum outer skin layer structure can be prepared by inducing the influent factors in the wet phase inversion system.
In the second part, this study focuses on the effect of polarity of coagulant on the inner skin layer formation and the influential factors on the final structure of hollow fiber membrane. It was found that the n-butanol was the best bore liquids and owns the well delay demixing behavior in membrane formation. The hollow fiber membrane with butanol as bore liquid effectively enhanced the inner skin layer thickness and also showed the good separation performance in dehydration of ethanol mixtures. On the other hand, the sulfonated polysulfone was used as the membrane material and utilized wet phase inversion method to prepare hollow fiber membrane with butanol as bore liquid. It was found that the polar polymer reduced the delay demixing behavior and limited the skin layer thickness. The decrease in separation performance with increasing the degree of sulfonation of polysulfone membranes was found in this case. The mixture bore liquid was considered for improving the delay demixing behavior of suffocated polysulfone membrane. Equal n-hexane and butanol were used as the mixed bore liquid in sulfonated polysulfone membrane preparation. It was found the delay demixing behavior significantly improved and formed a good skin layer structure. It is suggested that the mix solvents can be used as optimum polarity bore liquid in membrane formation and significantly improved the pervaporation performance.
It was concluded that the outer skin layer structure of hollow fiber membrane can be prepared by co solvent addition method and suitable polarity medium as the coagulant in membrane formation. It is indicated that the suitable bore liquid to form inner skin layer structure is superior to the outer skin layer formation method by considering the economic factors. This study had successful prepared the well inner and outer skin layer hollow fiber membranes by considering the membrane formation conditions and membrane formation methods.
